CS0246 error for Unity Packaged Scripts that are unable to be edited

Update3: Uninstalled Unity and Reinstalled. Then updated the game to the latest version of Unity. No change.

Update2: I am unable to add directives or references to the scripts, as they are auto updated from Unity whenever I make a change.

UPDATE: I am unable to edit the CS file in question. I have attempted making changes and adding assembly references, but the script auto updates and deletes any changes I make when I save it.

I originally had 30+ errors, and going to help>reset packages fixed most. I am down to six and have hit a brick wall. The following are the remaining error codes:

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(77,16): error CS0246: The type or namespace name 'ClipBlends' could not be found (are you missing a using directive or an assembly reference?)

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(167,59): error CS0246: The type or namespace name 'ClipBlends' could not be found (are you missing a using directive or an assembly reference?)

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(317,30): error CS0246: The type or namespace name 'ClipDrawData' could not be found (are you missing a using directive or an assembly reference?)

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(342,46): error CS0246: The type or namespace name 'ClipBorder' could not be found (are you missing a using directive or an assembly reference?)

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(17,9): error CS0246: The type or namespace name 'ClipDrawData' could not be found (are you missing a using directive or an assembly reference?)

Library\PackageCache\com.unity.timeline@1.4.5\Editor\treeview\ItemGui\TimelineClipGUI.cs(40,25): error CS0246: The type or namespace name 'IconData' could not be found (are you missing a using directive or an assembly reference?)

[1]: /storage/temp/190558-timelineclipguicsharp.txt